Wave transformation in the nearshore zone: comparison between a Boussinesqmodel and field data

A numerical model based on the Boussinesq equations was developed to simula te wave transformation in the nearshore zone with emphasis on describing th e effects of wave breaking. Two different formulations for estimating addit ional momentum due to depth-limited wave breaking, namely one proposed by W atanabe and Dibajnia [Watanabe, A., Dibajnia, M., 1988. A numerical model o f wave deformation in the surf zone. Proceedings of the 21st Coastal Engine ering Conference, ASCE, pp. 578-587] and another one by Schaffer et al. [Sc haffer, H.A., Madsen, P.A., Deigaard, R., 1993. A Boussinesq model for wave s breaking in shallow water. Coastal Engineering 20, 185-202], were incorpo rated and tested in the numerical wave model: Detailed, high-quality data f rom Duck, NC, collected during the DUCK85 and SUPERDUCK field experiments u sing photographic means were employed to evaluate the applicability of the Boussinesq model to surf-zone conditions. Also, comparison with the field d ata allowed for an assessment of how well the two formulations could descri be the effects of wave breaking on the evolution of the waveform. Model sim ulations were compared with measured time series of water surface elevation as well as with derived statistical quantities, such as the skewness, kurt osis and root-mean-square wave height. Overall, the model results were sati sfactory, although the Boussinesq model failed to accurately reproduce the strong nonlinear shoaling that occurred prior to breaking. The roller model developed by Schaffer et al. produced somewhat better agreement with the d ata than the model proposed by Watanabe and Dibajnia. However, the differen ce was small and both formulations are judged to yield acceptable results, although improvements are needed before the predictions can be used for cal culating the sediment transport rate in intra-wave models. (C) 2000 Elsevie r Science B.V. All rights reserved.